The present invention relates to a variable displacement swash plate type compressor adapted for use in an air conditioning system for a vehicle, and more particularly to an anti-rotation structure for pistons disposed in cylinders within the compressor to prevent rotation of the pistons in the cylinders.
Variable displacement swash plate type compressors typically include a cylinder block provided with a number of cylinders, a piston disposed in each of the cylinders of the cylinder block, a cylindrical crankcase sealingly disposed on the end of the cylinder block, a rotatably supported drive shaft, and a swash plate. The swash plate is adapted to be rotated by the drive shaft. In addition, the swash plate is operatively connected to a bridge portion of the pistons through shoes. Rotation of the swash plate is effective to reciprocatively drive the pistons. As the swash plate is rotated, frictional forces act laterally on the shoes, which cause the pistons to rotate within the cylinders. Rotation of the pistons must be restricted to prevent contact between the swash plate and the bridge portions of the pistons.
Prior art anti-rotation structures include a winged structure attached to the piston. The ends of the winged structure are designed to contact the inner surface of the crankcase to limit rotation of the piston. The entire winged structure is disposed to extend radially outwardly of the longitudinal axis of the piston from the peripheral surface of the piston. In order to accommodate the winged structure, the diameter of the crankcase must be large.
An object of the invention is to produce a swash plate type compressor having an anti-rotation structure that can be accommodated in a crankcase of a size smaller than the prior art structures.
Another object of the invention is to produce a swash plate type compressor that can be manufactured more economically than the prior art structures, and provide smooth operation and a long service life.
The above, as well as other objects of the invention, may be readily achieved by a variable capacity swash plate type compressor comprising a cylinder block having a plurality of cylinders arranged radially and circumferentially therein; a crankcase mounted adjacent the cylinder block and cooperating with the cylinder block to define a sealed crank chamber, the crankcase having a central axis and an inner wall with spaced apart longitudinally extending parallel bearing surfaces formed therein and extending parallel to the central axis of the crankcase, the bearing surfaces defining longitudinal recessed portions therebetween; a drive shaft rotatably supported by the crankcase and the cylinder block in the crank chamber; a swash plate slidably and rotatably disposed on the drive shaft; a plurality of pistons reciprocatively disposed in each of the cylinders of the cylinder block, each piston having a longitudinal axis and an outer surface, means for achieving a hinged connection between the swash plate and each of the pistons so that when the drive shaft is rotated, each piston reciprocates in the corresponding cylinder; and an anti-rotation structure disposed on each piston to reciprocatively move within the crankcase, the anti-rotation structure having two shoulder portions extending radially outward from the longitudinal axis of each piston to a point beyond the outer surface of each piston to slide adjacent the raised pads of the inner wall of the crankcase, the shoulder portions of the anti-rotation structure permitting the outer surface of each piston to reciprocatively move adjacent the recessed portions of the inner wall of the crankcase.